So I got a pretty bad misfire the other day (p0301) so I got new plugs ( some iridium stuff the guy said was really great and gapped at .40...) And a new coil. Got them in and still ran like dog shit. So I then switched the two injectors around and the misfire moved to cylinder 3( p0303). Cool. Bought 2 new injectors because I cracked the one during the switcheroo . Finish that tonight and stilllllllllllllll this damn misfire is there, except it was cylinders 1,3 and 4. Could spark plug gap be causing this? I checked grounds, plugs, battery terminals, and did the trusty carb cleaner test, and nothing is fixing it or givinge any new signs. Please help me!

"0.4" is not the right gap (also, use units when you state dimensions! 0.4 means nothing without a unit). The plugs should be gapped to 0.7-0.8mm (0.028-0.032in) per the FSM. There is no problem gapping iridium plugs, just don't leverage off of the electrode and you'll be fine (as in, the only thing you should be touching is the ground tab). The only reason the warning exists to not gap iridium plugs is because people aren't careful.

Update. Got new plugs from the dealership. Worst decision of my life but didn't have another option. Got them installed and still pulling the P0301 code. Horribly rough idle and can feel it through all the revs. And wants to die on deceleration.

I'm having a misfire also but it comes and goes. it will run great for a couple days and then start misfire and showing a code. I turn it off and start it the next day it runs fine again. I thought I seen somewhere that it may be a ground issue but don't know.

Update. Time for new heads. Bad valve guide on cylinder 3 and a burnt out exhaust valve on cylinder 1. F**k. My. Life.

Did you or someone else diagnose the problem? I ask because it seems like you went quickly from trying a simple fix (spark plugs) to having a serious problem that I think requires the head to have been removed to confirm the problem.

Gave up and went to a Subaru dealer. The mechanic has 20+ years of experience. He pulled my exhaust manifold off and you could actually see the one valve guide out of the head and then on the other one you could see the burnt up exhaust valve through the stethoscope .

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